Overview: The intermediate frequency induction furnace is also known as the intermediate frequency furnace . It is a power supply device that converts the industrial frequency 50HZ alternating current into the intermediate frequency ( 300HZ or higher to 1000HZ ). The three-phase power frequency alternating current is rectified and turned into direct current. Then, the direct current is changed into an adjustable intermediate frequency current, and the intermediate frequency alternating current flowing through the capacitor and the induction coil is supplied to generate a high-density magnetic line in the induction coil , and the metal material contained in the induction coil is cut in the metal material. A large eddy current is generated. Widely used non-ferrous and ferrous metal melt. Compared to other casting apparatus, medium frequency induction furnace having a high thermal efficiency, short melting times, less burning of alloying elements, wide melt material, on environmental pollution, can accurately control the temperature and composition of the molten metal and the like.

A good way to quickly select the " intermediate frequency furnace "

1 、 Selection of intermediate frequency furnace transformer capacity

The value of the transformer capacity = the value of the power supply of the intermediate frequency furnace x 1.2

Transformer rectifier transformer to reduce the harmonic interference, possible special plane, i.e., a furnace disposed intermediate frequency of a rectifier transformer.

2 , the selection of the intermediate frequency furnace incoming line voltage

For the intermediate frequency power supply for medium frequency furnaces below 1000KW , three-phase five-wire 380V and 50HZ industrial power are generally used . For medium frequency furnaces above 1000KW , the focus is on using 660V incoming voltage .

3 , according to the capacity requirements to determine the selection of large tonnage of the intermediate frequency furnace.

Liquid iron in a weight of each working day and the weight required for a single piece, may determine the capacity of the furnace IF furnace.

4 , the choice of furnace structure

The melting furnace for the aluminum alloy structure with the reducer as the tilting furnace is commonly known as the aluminum shell furnace. The induction melting furnace of the steel structure with the hydraulic cylinder as the tilting furnace is commonly called the steel shell furnace. The steel shell furnace is asteel structure , and the aluminum shell furnace shell material is an aluminum alloy .

5 , medium frequency furnace temperature control method

Generally use red ultraviolet thermometer + closed loop PID control to automatically adjust power and control temperature

The price of the intermediate frequency furnace :

The intermediate frequency furnace is mainly composed of four parts :

1, the power supply and electrical components: power supply apparatus includes a high voltage or low voltage switchgear, wherein there are frequency power supply control circuit chip motherboard i.e., three-phase power rectifier (SCR 6 by the rectified AC power into DC), an inverter section (4 a the SCR or 8 converts the DC voltage into a frequency of about 1000HZ IF) output by the electric capacitance. Power conversion switch, compensation capacitor and intermediate frequency control cabinet (furnace distribution console), etc., the electrical part of the large intermediate frequency furnace also includes the leaking furnace alarm system.  

2 , the furnace body part: the furnace body includes the furnace cover, the sensor, the crucible, the furnace body bracket and the like.

3. Transmission: The transmission includes the movement of the furnace cover and mechanical or hydraulic devices such as tilting and resetting of the furnace body.

4 , water cooling system: water cooling parts are: intermediate frequency power supply, sensors, capacitors and busbars, flexible cables. In order to save water, a method of circulating cooling is usually employed. The cooling water circulation system includes a water pump, a cooling tower, a water tank, and the like.

Five, medium frequency furnace power, tonnage, power consumption selection method :

Classification of intermediate frequency furnaces :

 medium frequency furnace can be divided into molten metal materials

1 , medium frequency copper melting furnace

2 , medium frequency aluminum melting furnace

3 , medium frequency melting furnace

4 , medium frequency melting iron furnace

5. Noble metal melting furnace,

 Medium frequency furnace can be divided into furnace body structure according to the outer shell material

1, steel shell intermediate frequency furnace

2, aluminum shell intermediate frequency furnace

What is the difference between an aluminum shell intermediate frequency furnace and a steel shell intermediate frequency furnace ?

Medium frequency melting furnace with a steel structure into the yoke and the aluminum hydraulic tilting furnace with the furnace tilting gear. usually

Steel shell furnace: It has long service life (normal normal service life is more than 10 years) and good stability. Because of the use of magnetizer, the magnetizer has two functions: first, the top wire of the magnetizer and the induction coil are firmly fixed, so that The coil and the magnetizer form a stable structure. Second, the magnetizer can form a magnetic permeability barrier around the coil; energy saving, because the furnace with the magnetizer saves 3%-5% compared with the aluminum shell furnace ; the casting is stable, and the hydraulic tilting device can well control the casting Angle, speed; good safety performance, due to the characteristics of the leaking alarm device and refractory rubber layer, its good characteristics are steel shell structure when the tonnage is more than 2T .

Aluminum shell furnace: Aluminum shell furnace is a simple structure, the service life is generally about 5-8 years, there is no magnetizer, furnace lining mechanism, refractory clay layer, its safety performance is poor, generally used with capacity below 2T . For example: a 5T medium frequency furnace, when the furnace is full of molten iron, the overall weight of the equipment reaches 8-10T . If the aluminum shell structure is selected, when the reducer rotates the furnace body to 95 degrees, the whole furnace body will lean forward, and the safety performance is very good. difference. The aluminum shell furnace is suitable for small tonnage users who change production in a short time.

 What should I pay attention to in the operation of the intermediate frequency furnace ?

The phase-frequency AC power is converted into DC power, and after the inverter circuit output is converted into a single-phase AC power, the metal is heat-treated according to the principle of electromagnetic induction. However, in order to ensure that the intermediate frequency furnace can operate efficiently, it is necessary to carry out safe operation. The following is a detailed description of how to carry out safe operation.

1 , precautions before opening the furnace

The intermediate frequency electric furnace must check the electrical equipment, the water cooling system, the inductor copper tube, etc. before the furnace is opened. Only when these several equipments are in good condition can the correct method of safe operation of the intermediate frequency furnace be analyzed.

IF forging and casting furnace is a thermal processing apparatus for the inverter unit of several parts, the furnace and furnace control other components of the furnace by three, to ensure the safety of the heat treatment, or prohibiting the opening of the furnace; specifically determining The person responsible for power transmission and opening, and the responsible person shall not leave the post without authorization. During the work, the external condition of the sensor and the cymbal must be supervised to prevent people from touching the sensor and cable after power transmission, which affects the normal operation of the intermediate frequency electric furnace. Work or a safety accident.

2 , precautions after opening the furnace

After the intermediate frequency furnace is opened, during the charging, the inside of the furnace should be inspected to avoid mixing with flammable and explosive materials. In order to prevent the occurrence of the capping phenomenon, it is strictly forbidden to directly add the cold material and the wet material in the molten steel, and after the molten liquid is filled to the upper portion, the bulk material should not be added ; in order to avoid the explosion accident, it is necessary to ensure the pouring place and the furnace. There is no water in the front pit, no obstacles . In the pouring, two people need to cooperate, and the remaining molten steel can only be dumped at the place where it is made, and cannot be dumped anywhere.

3 , precautions during maintenance

When maintaining the medium frequency electric furnace, the internal frequency generator room should be kept clean and the flammable and explosive materials should not be stacked. Repair the furnace with excessive melt loss in time, and avoid the incorporation of iron filings and iron oxide in the furnace to ensure the compaction of the crucible.

What are the main factors that cause the accident in the intermediate frequency furnace ?

The reasons for the intermediate frequency furnace explosion accident are:

1 . The presence of moist materials in the charge causes a steam explosion.

2 . Temperature sampling or lack of operating skills when adding alloys, causing splashes of molten metal.

3 . Injecting large metal materials into the furnace causes the molten iron to splash.

4 . Unreasonable feeding system leads to bridging.

5 . Failure to escape outside the safety line resulted in injury.

6 . Contact with the power conductor, safety interlock control failure or contact with incompletely discharged capacitors, etc., resulting in shock or death.

7 . Lack of proper safety training.

The main points of the intermediate frequency furnace steel

1 , the task of steel

The main raw material for melting is scrap steel and a part of pig iron. The purchased scrap has more rust, muddy sand and other dirt, and the content of sulfur and phosphorus in the steel is also high. The task of the steel is to smelt the raw materials of the above conditions into high-quality molten steel with low gas content, high inclusion content, qualified components and temperature. Specifically, the basic tasks of the steel are:

( 1 ) melting solid charge (cast iron, scrap, etc.);

( 2 ) making the elements such as silicon, manganese and carbon in the molten steel reach the specification components;

( 3 ) removing harmful elements such as sulfur and phosphorus and reducing their content below the specified limit;

( 4 ) removing gas and non-metallic inclusions in the molten steel to make the molten steel pure;

( 5 ) adding alloying elements (melted alloy steel) to meet the requirements;

( 6 ) The molten steel is superheated to a certain temperature to ensure the need for pouring;

( 7 ) In order to increase production and reduce costs, it is necessary to rapidly reduce steel;

( 8 ) Casting into a good casting.

2 , the method of steel

There are many methods for chemical steel, mainly including induction furnace steel, open hearth steel, and electric arc furnace steel.

Electric arc furnaces and induction furnaces commonly used in cast steel workshops. They have looser requirements on raw materials, higher quality of molten steel, and the steelmaking cycle is suitable for the characteristics of cast steel production. It is convenient to open and stop the furnace, and it is easy to coordinate with the progress of the process of molding and boxing. Organize production. In addition, the equipment for electric furnace steel is relatively simple, with less investment, and the infrastructure construction speed and capital recovery are fast.

In recent years, induction furnace steel has gradually developed. Induction furnace steel process is relatively simple, and the quality of molten steel can be guaranteed. Many factories use induction furnace steel to cast small castings, especially in investment casting foundries, and widely use induction furnaces to melt molten steel.

In the heavy machinery factory, flat furnace steel has been used so far. The capacity of the open hearth furnace is generally larger than that of the electric furnace. The flat steel can be used to produce a large amount of molten steel at one time, which is suitable for pouring large and complex heavy castings.However, the cycle of open hearth steel is long, and the time for producing a furnace steel generally takes more than six hours. The open hearth structure is large and complex, the output is low, and the quality of the molten steel is not as good as that of the electric furnace, so its development is greatly limited. In some countries, new open hearths are no longer built.

In recent decades, pure steel top-blown converters have been widely used in the steel industry to convert steel. This method of steelmaking is fast, high in productivity, and the quality of molten steel is also guaranteed. This type of furnace is more suitable for steel ingot production.

With the development of production and science and technology, new steelmaking methods for DC arc furnaces, vacuum induction furnaces and refining equipment outside the furnace have emerged, the quality of molten steel has been greatly improved, and the quality of castings has been greatly improved.

What are the factors that affect the energy consumption of the intermediate frequency furnace?

  Ten, factors affecting energy intermediate frequency furnace mainly in the following four points:

1 , power supply

The frequency density configuration of the intermediate frequency furnace is high. The configuration is high, the melting speed is fast, and the energy saving effect is good. Whether the intermediate frequency furnace can maintain high power and continuously send power to the furnace will affect the energy consumption; the intermediate frequency furnace power supply line is disorderly, which will affect the power processing capacity, resulting in unstable power, low power conversion efficiency, and influence energy. Consumption.  

2 , the melt

The cleanliness of the surface of the charge, such as 5 % impurities, will consume 5 % of the electrical energy to melt these impurities, and will affect the life of the lining; the appropriate length of the furnace block will affect the electrical efficiency and melting quality of the electric furnace, generally200 ~ 300mm block is suitable;

3 , refractory materials  

The use of a suitable crucible can increase the melting rate, the quartz crucible is resistant to high temperatures, and is used with an intermediate frequency furnace. The metal material in the crucible generates heat by induction heating, which can reduce the heat transfer consumption.

4 , improper operation causes high energy consumption  

The molten metal is overheated and the liquid is discharged from the furnace. Not only is it unsafe, it is also wrong in terms of energy consumption and melting process. Generally, the electric furnace sensor is divided into two parts. When the metal liquid level in the furnace is lower than half of the upper inductor, the upper inductor no longer has an induced current passing due to the resistance change, and all of the lower inductors are concentrated in the lower inductor to make the lower metal liquid. Overheating, flushing the furnace wall, the life of the lining drops sharply.

 How is the intermediate frequency furnace more power efficient?   ?

1. Under the premise of ensuring the reasonable operation of the workers, the rationality of the layout, and the overall layout of the electric furnace, we should minimize the space layout to shorten the overall connection line, which will reduce the loss of thermal power and save electricity.

2 , the material used should be as large as possible to ensure a smooth flow of current to prevent the copper row too small, causing the heat to take away part of the power.

3, to be diligent workers, and to continue feeding the auxiliary stirring steel, increase the speed of melting, saving power consumption

4 , the technical content of the intermediate frequency furnace, this point is not well determined by the manufacturers. Although the intermediate frequency furnace technology is relatively mature, each family still has its own certain advantages. Therefore, manufacturers are advised to choose large manufacturers to cooperate when purchasing electric furnaces. Make sure you save on power consumption.

XII yoke IF furnace temperature is too high what is the reason?

The yoke redness is a common failure phenomenon in the operation of the intermediate frequency power supply. First check if there is any problem with the cooling water system, check whether the red yoke inlet and outlet water is normal, and whether the pipeline is aging or leaking. If it is normal, check the following aspects.

(1) The yoke of the intermediate frequency power supply is aging, and the interlayer insulating coating is severely corroded. For this, the silicon steel sheet can be opened for surface coating treatment.

(2) The yoke is adhered to the molten steel (iron filings), and the yoke can be polished to remove the adhered iron filings.

(3) Check the thickness of the bottom of the furnace. If the bottom of the furnace is too thick, it will cause the yoke to heat up and become red.

(4) The temperature of the circulating water inlet water is too high, and the water temperature inside the yoke circulation system is too high to generate gas. Since the gas cannot be discharged, the circulating water cannot circulate, causing the temperature to rise.

5 ) The circulating water pressure becomes smaller, or after the waterway is changed, the waterway becomes more or the water pipe becomes larger, and the water flow of the other circuits becomes larger, causing the yoke water flow to become smaller.

Thirteen, is the IGBT intermediate frequency furnace really more energy efficient than the SCR intermediate frequency furnace?

Under the same conditions, the IGBT electric furnace saves 0.0976 % more energy than the SCR electric furnace , which is almost negligible.

IGBT is a new type of switching device, with fast switching speed, plus control signal conduction, eliminating control signal cut-off, convenient control, reduced conduction voltage and low power consumption. The maximum current of the IGBT is only 2 times the rated current, the impact resistance is poor. SCR is a traditional switching device with high control power and high impact resistance. Is the IGBT electric furnace really more energy efficient than the SCR electric furnace ? We can see whether the power is saved by the following calculation.

　　 1 t The power of 500KW electric furnace, into the phase voltage 380V, IGBT electric power factor is 0.98, the DC current is 928A, the power consumed by the IGBT 4 [1V (IGBT conduction voltage drop) X 　 928A/2] 　 X 　 4=1856W=1.856KW ; SCR electric furnace has a power factor of 0.93 and DC current is 977A. The power consumed by SCR is: [1.2V ( SCR conduction voltage drop) X977A/2] 　 X 　 4=2344W=2.344KW. It can be seen that the power consumed by the IGBT is 21 % lower than the power consumed by the SCR .

It is concluded that the IGBT electric furnace saves 21 % compared with the SCR electric furnace . It is wrong. We continue to calculate that the power consumed by the IGBT is 1.56KW/500KW=0.003712=0.3712% of the total power ; the power consumed by the SCR is the total power. The percentage is2.344KW/500KW=0.004688=0.4688%. It can be seen from the above calculation data that under the same conditions, the IGBT electric furnace saves 0.0976 % compared with the SCR electric furnace , which is almost negligible.

If other conditions are changed, the IGBT electric furnace adopts series inverter, and by increasing the intermediate frequency voltage to save electricity, that is another matter. SCR electric furnace can increase the intermediate frequency voltage by 2 times voltage. Since the withstand voltage and current of SCRare much higher than IGBT devices, SCR electric furnace can adopt high phase voltage and high intermediate frequency voltage. Therefore, SCR electric furnace is reasonable in design and expensive IGBT. Electric furnaces should be more energy efficient.

14. What information does the customer need to provide to the supplier before purchasing the intermediate frequency furnace ?

1. 1t intermediate frequency furnace should have layout space, need to provide the area and layout of the plant

2. The customer needs to provide the capacity of the transformer, the magnitude of the incoming line voltage, and the frequency of the incoming line voltage.

3. The intermediate frequency furnace needs water cooling equipment, and the configuration of 1t medium frequency electric furnace contains water cooling equipment.

4. The structure of the medium frequency furnace has a steel shell body and an aluminum shell body, which requires the customer to specify the furnace structure.

5. The power supply of the intermediate frequency furnace is the intermediate frequency power supply. The line structure of the intermediate frequency power supply is divided into the inverter parallel and the inverter series structure. The inverter series structure is energy-saving, the power factor is 0.9 6 , and the line is stable. The inverter parallel structure is of the common type with a power factor of 0.92, which requires the customer to specify the line structure.

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